The pulse inversion (PI) method has been known as the method for achieving high image quality of the ultrasound image. The PI method is called phase inversion method as the technique for ultrasound imaging with a harmonic content (harmonic) by utilizing nature of the ultrasound resulting from irradiating the living body organ with ultrasound at the single frequency. Specifically, upon ultrasound irradiation, the fundamental wave of the reflection ultrasound reflects at the same frequency with the same polarity as the irradiated ultrasound. On the contrary, the harmonic content of the reflection ultrasound reflects with monopolar regardless of polarity of the irradiated ultrasound. More specifically, a first reflection ultrasound (including the first fundamental wave content and the first harmonic content) as a result of irradiation of the first transmission waveform (positive electrode) is received, and a second reflection ultrasound (including the second fundamental wave content and the second harmonic content) as a result of irradiation of the second transmission waveform (negative electrode) is received, which has been derived from reversing polarity of the first transmission waveform (or phase shift at 180°). Addition of the first and the second reflection ultrasounds will offset the first and the second fundamental wave contents, making the first and the second harmonic contents doubled. Consequently, the PI method is carried out on the assumption that the sum of the first transmission waveform (positive electrode) and the second transmission waveform (negative electrode) is zero with respect to those frequency contents such as the fundamental wave and the harmonic content. If the assumption is ineffective, image quality is deteriorated, or in some cases, artifact (false image) is generated. In the transmission-reception circuit system of the actual configuration of the device, the positive-negative asymmetry (the sum of the first and the second transmission waveforms is not zero) is caused by various factors.
Various proposals for retaining the positive-negative symmetry have been made by, for example, Patent Literature 1 disclosing the transmission circuit suitable for carrying out the PI method, Patent Literature 2 disclosing structure of the oscillator for efficiently receiving the harmonic content, and Patent Literature 3 disclosing the method of processing the reception signal utilizing the filtering method.